OpenStreetMap originally permitted anonymous edits, meaning edits with no form of attribution identifying a user.
OpenStreetMap still allows complete anonymity in so far as anyone can create an account and edit the map. You can choose any username you like - let's say "Mapper32". No-one need find out who you really are!
Originally though, you could edit without even having the edits attributed to "Mapper32".
Unfortunately, this meant that anonymous mappers - usually accidentally - could delete other people's hard work, and it was impossible for anyone to contact them. If experienced OpenStreetMap users had the chance to contact such users, via the site's own message system, then they could help them to avoid such mistakes, reducing the chances of work being deleted.
Anonymous editing phased out
In 2007 we changed it so that any newly registering users were not be able to put their account into this mode. We also disallowed use of anonymous editing accounts via the online editor (Potlatch) at this time. The result was that the vast majority of users did not remain in an anonymous mode, but as of April 2009 all users were be forced to leave anonymous editing mode if they wish to make further edits using any editor. See the mailing list announcement
I am in anonymous mode. How can I carry on editing?
Firstly this only affects the tiny minority of people who joined OSM before 2007 and are still in anonymous editing mode. If you are not one of these people, you can stop reading now!
Log into the main site as usual, then click on your username at the top right of the screen. Click "my settings". click the button "Make my edits public".
The "Make my edits public" button means that your edits on OpenStreetMap (including past edits) will be attributed to your user account. Your display name will appear alongside the edits, and people will be able to see these and send you a message via the website.
This is the way it is already set up for the vast majority of OSM users. The change brings us more into line with successful communities like Wikipedia. If you have an account at Wikipedia, your username is always described in the history of pages you edit, and people can send you messages. Even if you don't have an account, your IP address (your computer's unique identifier on the Internet) is marked, which people can use to send you messages via Wikipedia.
If you have only edited map data in the area you live in, then people will be able to look at your set of edits and get a rough idea of where you live, but remember, it's only your mapping username that is associated with changes to the map. If you don't want anyone to find out who Mapper32 really is, they won't. If you are concerned about people discovering your real name, or cross correlating information from other online communities where you use the same name, you could always change your display name to something more anonymous. This comes with its own disadvantages. Using real names or sticking with the same identity across several websites helps you build up reputation and trust.
For uploading GPS tracks, note that your username is not associated with your GPS tracks, unless you expressly click "public" for each track.
If you don't want to click the "Make my edits public" button, your only alternatives are to (A) Make no further edits to OpenStreetMap or (B) Leave your anonymous account lying dormant, and register a new user account (which will not be in anonymous editing mode) This is not recommended. We strongly encourage you to stick with one user account for one user, and simply click "Make my edits public" without worrying about it, for all the good reasons outlined above.